This invention relates to the detection and measurement of a gas in an atmosphere, and more particularly this invention relates to the operation and use of an emission spike train as produced by a long pulse output mode of a solid-state laser as a remote sensor of atmospheric gases.
The use of lasers for the remote sensing of atmospheric gases by differential absorption techniques is already known. Lidar and transmission measurements require at present, however, that the laser source used be tunable (continuously or discretely) on and off the absorption line of the gas being sensed. It should be noted here that these tunable lasers are expensive. Also these laser sources have repetitive pulse rates as well as changes from on to off line wavelengths which are slow compared to changes in the atmosphere. The net result is a decrease in the magnitude of the signal-to-noise ratio over a measurement technique which can essentially simultaneously measure the on and off line absorption.
There is, thus, a need for a method and apparatus for the remote sensing a atmospheric gases such as methane which can utilize existing equipment and which does not require the cumbersone and expensive equipment and techniques of the prior art. The present invention has been found to satisfy this need.